Maternal smoking is responsible for 30 percent of low birth weight infants, 10 percent of premature deliveries, and 5 percent of all infant deaths in the United States. Smoking cessation during pregnancy substantially reduces these risks. Unfortunately, even with augmented behavioral counseling interventions, the rate of smoking cessation during pregnancy averages only 13 percent. These low quit rates may be due to inadequate treatment of nicotine addiction. Indeed, medications are routinely recommended for smoking cessation treatment in non-pregnant smokers; however, little data are available on the safety and efficacy of medications to help pregnant women quit smoking. This application responds to a NIDA Program Announcement (PA 07-329) for research to Determine the best treatment practices for the use of pharmacotherapy in the treatment of pregnant women in terms of both mother's and the infant's health. This project will examine the safety and efficacy of the nicotine inhaler as an aid to smoking cessation during pregnancy. The specific aims are: (1) To examine the efficacy of the nicotine inhaler compared to a matching placebo for smoking cessation and reduction during pregnancy; (2) To compare the nicotine inhaler with placebo on overall nicotine exposure (as reflected by serum cotinine concentrations), and on birth outcomes (i.e., birth weight and gestational age); (3) To identify factors that determine which women benefit most from the use of the nicotine inhaler for smoking cessation during pregnancy; (4) To explore mechanisms by which the nicotine inhaler increases birth weight and gestational age. Subjects will be recruited from prenatal clinics that serve primarily a low-income, minority population. Pregnant smokers (n=360) who smoke at least five cigarettes/day will receive nurse-delivered behavioral counseling and be randomized to receive a 6-week course of treatment with either a nicotine inhaler or placebo, followed by a 6-week taper. Birth outcomes will be obtained on all participants. The investigators hypothesize that, compared with placebo treatment, the nicotine inhaler will result in: 1a) higher 7-day point prevalence abstinence rates; 1b) fewer cigarettes smoked per day at 32-34 weeks gestation; 2a) lower cotinine concentrations at these two time points; 2b) higher birth weight infants and 2c) longer gestational age and fewer low-birth-weight and preterm deliveries; (3) greater benefits among heavier smokers (> 10 cigarettes/day) than lighter smokers; (4) evidence that smoking cessation or reduction explains greater birth weight, which may be mediated by changes in markers of inflammation or endothelial function. This study builds on prior work and holds promise for increased understanding of the safety and efficacy of the nicotine inhaler for smoking cessation during pregnancy.